Acoustic device



Oct. 6, 1936. SHOWER 2,0565300 ACOUSTIC DEVICE Filed May 31, 1934 FIG.2A. 2/

lNl/ENTOR E. 6. SHOWER 8V I OM26 6. M ATTORNEY Patented Oct. 6, 1936UNITED STATES PATENT OFFICE.

Bell Telephone Laboratories,

Incorporated,

New York, N. Y., a corporation of New York Application May 31, 1934,Serial No. 728,406

2 Claims.

15 ing, when in use, to force thevibratory member away from the receivermagnet structure.

Still other features will be apparent from the detailed descriptionwhich follows hereinafter.

An acoustic device inaccordance with this invention comprises,preferably, a flattened magnet structure having pole-pieces, an armaturenormally lightly pressed against or in contact with the faces of thepole-pieces, an elongated, vibrations-conducting rod connected at oneend to the armature and terminating at its other end preferably in abutton-shaped member adapted to engage with the mastoid eminence of theuser, and means, for instance, a spring, member, for supporting the rodand armature. In operation, the 30 button-shaped member is pressed,preferably,

against the users mastoid eminence, and the armature is forced away fromthe pole-pieces. The gap between the pole-pieces and-the armature, withthis arrangement, may be maintained at a minimum for emcient operation.

A modification of the invention comprises an acoustic device having acasing enclosing a magnet structure having pole-pieces, and supporting astiff strip of magnetic material on its rim por- 40 tion and adjacentthe faces of the pole-pieces in contact therewith or spaced slightlytherefrom.

An elongated, vibrations-conducting rod or memwhich follows, read withreference to the appended drawing, wherein:

Fig. 1 is a sectional view of a bone conduction receiver embodying thisinvention;

Fig. 2 is a sectional view of the device of Fig. 1 5 taken along theline 22 thereof;

Fligs. 2A and 2-3 are enlarged views of a fragment of the device of Fig.1 and show the position of the receiver armature when the device is notin use and when it is in use, respecl0 tively;

Fig. 3 shows how a receiver embodying this invention would be used;

Fig. 4 is a sectional view of another embodiment of this invention; 2

Fig. 5 is a sectional view of the device of Fig. 4 taken along the line55 thereof;

Fig. 6 is a sectional view of still another embodiment of thisinvention, and

Fig. 7 is a plan view of the device of Fig. 6 with the cover memberremoved.

The acoustic device of Figs. 1-3 comprises a. bone conduction receiver,designated generally IIl,

' comprising a case or enclosure I I having an open end closed by acover member I2 held in place by any suitable fastening means, forinstance, screws I3. The case contains a substantially U shapedpermanent magnet I4, for instance, of co-' balt steel, pole-pieces I5,for instance, of silicon steeLbeing secured to the end portions I6 ofthe magnet by any suitable means, such as the screws II, the adjacentportions of the magnet and polepieces being clamped between the ridgeportion I8 on the wall portion I9 of the case, and the ridge portion 20on the cover member I2. The adJacent but spaced end portions 2I of thepole-pieces are bent substantially at right angles. An energizingwinding comprising coils 22 is supported on the pole-pieces, and isconnected with a source of sound wave frequency electric signal impulsesthrough the conductors 23. An armature member 24 of any suitablemagnetic material, normally in contact with and pressed lightly againstthe bent end portions of the pole-pieces, is connected at its midportionto a vibrations-conducting or bronze, bowed in a direction away from thearmature, attached at its mid-portion to the rod 25 intermediate thearmature and button member, and at its extremities to the pole-pieces byany suitable means, such as the screws 30.

In use, the receiver in is mounted as shown in Fig. 3 so that pressureis exerted on the button member to force the armature away from the endsof the pole-pieces as indicated in Fig. 2-8.

Since the reluctance of the magnetic path is at a minimum when theair-gap length is a minimum, it is obvious that the efficiency of thereceiver will be at a maximum for the lightest pressure at which thereceiver will operate at all. Since the armature is forced away from thepole-pieces, it is obvious, of course, that there is no tendency for thearmature to freeze to the pole-pieces'while the receiver isin use.

In the bone conduction receiver of Figs. 4 and 5, the end portions 3| ofthe substantially U shaped permanent magnet 32 are secured to the endportions 33 of the pole-pieces l by any suitable fastening means, suchas screws 34, the case 35 being provided with grooves 36 to receive theend portions of the pole-pieces and magnet which are clamped between theshoulders 31 and the case cover member 38. This receiver is otherwisethe sameas that of Figs. 1 to 3.

The acoustic device of Figs. 6 and 7 comprises a bone conductionreceiver, designated generally 40, comprising a case or enclosure 4|having an open end 42 closed by a cover member or cap '43, threadedlyengaging the wall portion 44 and clamping a vibratory strip or armature45 of any suitable magnetic material across the open end of the case andgainst the rim 46 thereof. A vibrations-conducting member or elongatedrod 41 is connected at one end 48 to the armature at a pointintermediate the mid-portion and one end of the armature, and extendsthrough an aperture 49 in the end wall 50 of the case to terminate in anenlargement or button member 5| adapted to engage with the mastoideminence of a user's head. Within the case are disposed a permanentmagnet 32, arcuate in shape and being, for instance, of cobalt steel, 9.pair of L shaped pole-pieces 53, for instance, of silicon steel, and anenergizing winding comprising coils 54 wound on the vertical portions ofthe polepieces. The ends of the pole-pieces are lightly engaged by thearmature which, when the receiver is in use, is forced away from thepolepieces, the armature being vibrated in accordance with the soundwave frequency electric signal impulses passing through the energizingwinding, these vibrations being communicated to the user by thevibration of his head bones.

While this invention has been disclosed with reference to severalspecific embodiments thereof, it is to be understood that variousmodifications in structure are possible without departing from theinvention, the scope of which is to be considered as limited by theappended claims, only.

what is claimed is:

1. A bone conduction receiver comprising a magnetic structure having areentrant pole-piece portion, an energizing winding for said structure,an armature between said reentrant portion and another portion of thestructure, -means connected to said armature for transferring itsvibrations to the head bone structure of a user, and a single, bowedspring supported on said pole-piece portion and supporting said means.

2. A bone conduction receiver comprising a magnetic structure having apermanent magnet and pole-pieces projecting toward and whose pole-facesare spaced from the permanent magnet, an energizing winding for saidstructure, an armature between said pole-pieces and said magnet, meansconnected to said armature for trans- 4 ferring the armature vibrationsto the head bone structure of the user, and means supported on thepole-pieces and supporting said vibrations transferring means, saidmeans comprising a single, bowed spring.

\ EDMUND G. SHOWER.

